Symptoms of a bad map sensor?

Posted by jdmawd, Dec 2, 2002
Tuning & Engine Management - 4G63 EPROMS, ECU, MAF, knock, EGT, wideband, datalogging, fuel trims, etc. Read this Forum's Strict Guidelines.

  1. jdmawd

    jdmawd Banned Member

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    GreenBelt, DC_Metro
    anyone ever had a map sensor go bad, if so what were the symptoms. here is the deal under part throttle or wot. it seems like the map sensor is not reading the increase in manifold pressure. while the turbo is spooling, until full boost is reached. i have checked the tps and it reads correctly. basically pressing the gas pedal and watching the percentage value on the s-afc progressively from 0-100%. fuel pressure is consistent and linear as the boost level rises. It appears that for some reason the vpc is not adding fuel until full boots is reached. also there is huge amounts of knock in the area also. The a/f gauge goes from cycling to red to no bars at all until full boost is reached, then knock goes away and the a/f gauge reads normally again. also i have tried different vacuum source location with the same effects. will map sensor line length, effect the sensors ability to read manifold pressure. the hkc hand books asks for 4" total length. mounting the map sensor on the fire wall, above the manifold makes that impossible.
     
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  2. jw

    jw Proven Member

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    The manual states how to check if the MAP sensor is working correctly. You can use a bicycle pump to pressure the sensor to see if the voltage are within specs. I know at atmospheric pressure (gauge pressure at 0psi), it should read around 1.74v.
     
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  3. jdmawd

    jdmawd Banned Member

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    GreenBelt, DC_Metro
    cool thanks
     
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  4. NJGSX96

    NJGSX96 Proven Member

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    YMB, New_Jersey
    I have the manual on my site if you want to check...

    http://www.databurstpc.com/data/hks_vpc_manual.pdf

    Tuning the AFC by MAPp is a little different than by TPS.

    What is the gain and response set to on the VPC?
    What is the HI/LO throttle positoin at on the AFC?
    What are the LO settings on the AFC?
    What are the HI settings on the AFC?
     
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  5. jdmawd

    jdmawd Banned Member

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    GreenBelt, DC_Metro
    i still have it wired up in the conventinal configuration. basically the safc intercepts the gray air flow wire from the vpc harness going to the ecu.


    gain is at 12 response is at 5
    LO throttle is 30% HI is 70%

    LO settings are-17 across the board
    HI starts at -15 and prgressivly ends at -8 by 7K

    base fuel pressure 38

    base timing is 5*

    boost level is 22 psi
     
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